To kick off the 2012 campaign, the Bears traded two third round picks to the Miami Dolphins for Marshall. He responded that year by breaking franchise records in catches (118) and receiving yards (1,508). He followed that up in 2013 with a 100-catch, 1,295-yard season, along with a club-record 12 touchdowns.

Based on his on-field production alone, Marshall was absolutely worth every penny that went into his extension. Yet it goes far beyond just his numbers as a receiver, and when looked at as a whole, it can be argued that the Marshall extension is easily the best move GM Phil Emery has made the entire offseason.

Marshall is one of the most dominant receivers of his generation. Since joining the league in 2006, he ranks third in the NFL in catches (712), fifth in receiving yards (9,050) and sixth in receiving touchdowns (57). Those are elite numbers no matter how you slice it, yet they are even more amazing when you consider the revolving door of mediocre quarterbacks Marshall has dealt with throughout much of his career.

When you can post back-to-back 80-catch, 1,000-yard seasons with Matt Moore and Chad Henne slinging passes, you know you're special.

Yet that's just the tip of the iceberg, as Marshall's value to the Bears runs much deeper.

First, consider his blocking ability. Pro Football Focus graded Marshall the best blocking receiver in the NFL last season, and it wasn't even close. From a recent PFF article:

"On receiving alone Marshall would still have made the list but ranked a ways lower. He still had a phenomenal year (as does anyone who makes this list) with impressive touchdown (12), broken tackles (13) and yards (1,295) telling part of the story. But what propelled Marshall from a man who would have our fifth highest receiving grade to top overall receiver, was his unmatched run blocking. And when we say unmatched we mean that in our six years grading nobody has ever come close, with it being nearly three times as much as the next highest graded receiver. Rarely does a receiver contribute on every down, but Marshall was that rarity."

Last year, Matt Forte was one of the league leaders in rushing yards, yards from scrimmage, first downs and rushing touchdowns, and Marshall's downfield blocking played a big role in Forte's success.

In addition, Marshall has become the ultimate team leader. Last offseason, he invited Alshon Jeffery to train in Florida, where Marshall lives. The result was a breakout season for Jeffery – 89 catches, 1,421 yards, 7 TDs – which earned the second-year player his first trip to the Pro Bowl.

Marshall and Jeffery finished second in the league with 2,716 combined receiving yards, which also set a franchise record. They became just the second receiver combo in Bears annals to each finish with 1,000 or more yards.

Credit again must go to Marshall for helping Jeffery transition into one of the most dangerous pass catchers in the NFL.

And there's no reason to believe either player will slow down, despite the fact Marshall turned 30 in March. While running backs tend to wear down in their 30s, receivers, particularly the elite ones, tend to carry their top-tier production far deeper into their careers.

The following is the four-year production of some of the NFL's best all-time receivers between ages 30-33:

Assuming he stays healthy, Marshall should continue to be one of the league's top receivers throughout the remainder of his extension.

Finally, Marshall comes at a bargain the next four years. In 2014, he'll make $9.3 million and will average just $10 million per season the next three years. That's extremely cheap for a player of Marshall's caliber, especially when you consider the yearly contracts of the following NFL receivers:

When you can get Marshall, who every year outshines every receiver on this list not named Fitzgerald or Megatron, you know you're getting an amazing bargain.

Think about it, the Chiefs will be paying Dwayne Bowe, who hauled in 57 catches for 673 yards last year, $1 million more than Marshall. The same goes for Harvin, whose on-field dependability is akin to loaning money to a drug addict. Marshall at $10 million is an absolute steal.

For all of Marshall's positives, he does come with an extensive rap sheet, one that includes multiple incidents of violence against women. By no means is he a saint but in his two-plus years in Chicago, Marshall has been a first-class citizen and team-first player. He's kept his nose clean off the field and he's worked harder than anyone to help the team on the field. You can't ask for much more than that.

All in all, it's nearly impossible to find a wide receiver in the NFL other than Marshall who produces at an extremely high level in every aspect of the game. And for $10 million a season, there's no pass catcher in the league who does as much for so little.

Say what you will about his past, if Marshall continues at his current pace, both on and off the field, he'll go down as the 33rd Chicago Bears player to be inducted into the NFL Hall of Fame.

For all those reasons, extending Marshall through 2017 is the best move Emery has made in six months, one that will pay big dividends the next four years.